Flash memory device and method of controlling flash memory device

ABSTRACT

A flash memory device includes multiple memory blocks, a decoder configured to select at least one of the memory blocks in response to block select signals, a controller configured to generate the block select signals in response to a block address and to generate a flag signal when the block address corresponds to a bad block, and an output buffer configured to output fixed data in response to the flag signal indicating that the block address corresponds to the bad block. When the block address corresponds to a bad block, the controller generates the block select signals to cause the decoder to interrupt selection of a memory block corresponding to the block address.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.12/109,466 filed on Apr. 25, 2008, which issued as U.S. Pat. No.7,768,831, on Aug. 3, 2010, which claims priority from Korean PatentApplication No. 10-2007-0040502, filed on Apr. 25, 2007, in the KoreanIntellectual Property Office, the disclosures of which are herebyincorporated by reference in their entireties.

BACKGROUND

The present invention disclosed herein relates to a semiconductor memorydevice and more particularly, to a flash memory device and controlmethod of a flash memory device.

Semiconductor memory devices are generally classified as volatile ornonvolatile. Advantages of volatile semiconductor memory devices includerapid read and write speeds, and disadvantages include losing storedcontents when power is removed. In comparison, nonvolatile semiconductormemory devices are able to retain stored contents, even when power isremoved. Therefore, nonvolatile semiconductor memory devices are usedfor applications that require contents to be stored regardless ofwhether power is continually applied. Nonvolatile semiconductor memorydevices include, for example, mask read-only memory (MROM), programmableread-only memory (PROM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), and thelike.

Some non-volatile memories, however, such as MROM, PROM and EPROM, cannot to be erased or written to by a system itself, so it is difficultfor general users to update stored contents. On the other hand, EEPROMis capable of being electrically erased or written. Accordingly, EEPROMapplications have widened to auxiliary memories and system programmingrequiring continuous updates (e.g., flash EEPROM). Flash EEPROM exhibitshigher degree of integration than conventional EEPROM, and is thereforeparticularly suited for large auxiliary memory applications. A NAND-typeflash EEPROM (hereinafter, referred to as a NAND flash memory device) ismore highly integrated than other types of flash EEPROMs.

In general, a flash memory device is an integrated circuit configured tostore information and to read stored information, as needed. A flashmemory device may include multiple memory cells having re-writingcapabilities. Each of the memory cells may store single-bit data ormulti-bit data. A flash memory device may have increased functionalitydue to high integration, large volume, and the like. Although this trenddecreases minimum feature size, it may increase complexity and thusreduce chip yield.

Therefore, a flash memory device may include redundant memory cells forreplacing defective memory cells, as well as means for switching anaddress of a defective memory cell to an address of a redundant memorycell. If a bad block having defective memory cells is detected duringtesting, a row decoder may be set so that the bad block is not selected.The row decoder may include a block decoder for selecting rows in ablock unit. The block decoder includes a fuse or a latch circuit that isset to interrupt accessing a bad block.

FIGS. 1A and 1B are circuit diagrams showing conventional block decodersconfigured to interrupt access to a bad block. FIG. 1A shows an exampleof a block decoder configured such that a bad block is processed basedon whether a fuse 12 is programmed. FIG. 1B shows an example of a blockdecoder configured such that a bad block is processed based oninformation stored in a latch 22.

Referring to FIG. 1A, a memory block is treated as a bad block bycutting the fuse 12 of block decoder 10. In this case, although blockselect signals Pi, Qi and Ri for selecting the memory block all arehigh, an output signal of NAND gate 11 is not transferred to node N1when the fuse 12 is cut. Accordingly, the node N1 has a high level and anode N2 has a low level. As a result, selection of the bad block isinterrupted, since a string select line SSL is grounded and a block wordline BWL is set to a low level.

Referring to FIG. 1B, data indicating a bad block or a normal block maybe stored in the latch 22 of block decoder 20. Logic “1” may be storedin the latch 22 to indicate a bad block and logic “0” may be stored inthe latch 22 to indicate a normal block. When logic “1” is stored in thelatch 22 of the block decoder 20, the logic “1” is sent to an inputterminal of NOR gate 23. Node N3 is therefore set to a low level,regardless of the values of block select signals Pi, Qi and Ri.

As illustrated in FIGS. 1A and 1B, conventional block decoders include afuse or a latch circuit for managing a bad block. However, such blockdecoder configurations increase complexity of the memory device and sizeof the row decoder. When a block decoder includes a fuse, the number ofbad blocks may increase due to instability of fuse programming. When ablock decoder includes a latch, an error may arise in an initialoperation during which bad block information is stored in the latch. Aflash memory device may further include means for writing data in alatch incorporated in the row decoder. Accordingly, a flash memorydevice is needed that is capable of managing bad blocks by means of asimple row decoder structure.

SUMMARY OF THE INVENTION

The present invention is directed to provide a flash memory device andcontrol method capable of performing a repair operation withoutinputting bad block information into a row decoder.

One aspect of the present invention provides a flash memory device,which includes multiple memory blocks, a decoder configured to select atleast one of the memory blocks in response to block select signals, anda controller configured to generate the block select signals in responseto a block address. When the block address corresponds to a bad block,the controller generates the block select signals to cause the decoderto interrupt selection of a memory block corresponding to the blockaddress.

Another aspect of the present invention provides a flash memory device,which includes a cell array having multiple memory blocks; a redundantcell array having one or more redundant blocks; and multiple blockdecoders, corresponding to the memory blocks, for selectingcorresponding memory blocks in response to block select signals,respectively. The flash memory device also includes a repair controllerfor generating the block select signals in response to a block addressand a redundant block decoder for activating a redundant block of theone or more redundant blocks when the block address corresponds to a badblock. Each of the block decoders has no storage unit for storing badblock information. Also, the repair controller generates the blockselect signals to interrupt selecting the bad block.

Still another aspect of the present invention provides a method ofmanaging a bad block in a flash memory device, including a memory blockand a block decoder for selecting the memory block in response to ablock select signal. The method includes comparing an input blockaddress with a bad block address, which indicates a defective memoryblock; generating a flag signal when the input block address correspondsto the bad block address; and generating an output signal in response tothe flag signal, the output signal externally indicating that the blockaddress corresponds to the bad block address. The block decoder does notstore information indicating the defective memory block.

BRIEF DESCRIPTION OF THE FIGURES

Non-limiting and non-exhaustive embodiments of the present inventionwill be described with reference to the attached drawings, in which:

FIGS. 1A and 1B are circuit diagrams showing conventional blockdecoders;

FIG. 2 is a block diagram showing a flash memory device, according to anexemplary embodiment of the present invention;

FIG. 3 is a circuit diagram showing a block decoder illustrated in FIG.2, according to an exemplary embodiment of the present invention;

FIG. 4 is a circuit diagram showing a disable circuit illustrated inFIG. 2, according to an exemplary embodiment of the present invention;

FIGS. 5A to 5C are circuit diagrams showing a predecoder illustrated inFIG. 2, according to an exemplary embodiment of the present invention;

FIGS. 6A to 6C are timing diagrams for read, program and writeoperations, according to exemplary embodiments of the present invention;

FIGS. 7A to 7C are timing diagrams for read, program and writeoperations, according to exemplary embodiments of the present invention.

FIG. 8 is a timing diagram for a read operation, according to exemplaryembodiments of the present invention.

FIG. 9 is a block diagram showing a flash memory device, according toanother exemplary embodiment of the present invention.

FIG. 10 is a circuit diagram showing a disable circuit illustrated inFIG. 9, according to an exemplary embodiment of the present invention.

FIG. 11 is a block diagram showing a memory card including a flashmemory device, according to exemplary embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. The invention, however, may be embodied in variousdifferent forms, and should not be construed as being limited only tothe illustrated embodiments. Rather, these embodiments are provided asexamples, to convey the concept of the invention to one skilled in theart. Accordingly, known processes, elements, and techniques are notdescribed with respect to some of the embodiments of the presentinvention. Throughout the drawings and written description, likereference numerals will be used to refer to like or similar elements,unless otherwise specified.

FIG. 2 is a block diagram showing a flash memory device, according to afirst illustrative embodiment of the present invention.

Referring to FIG. 2, a flash memory device 100 may include a row decoder140, which does not include a fuse or a latch (such as those illustratedin FIGS. 1A and 1B) indicating a bad block. Regardless, the flash memorydevice 100 is capable of performing a repair operation with respect tobad blocks, in particular, by means of control system including a repaircontroller 110, a disable circuit 120 and a predecoder 130.

The repair controller 110 determines whether an input block addressBLK_Add corresponds to a bad block. When the block address BLK_Addcorresponds to one of k bad blocks, the repair controller 110 outputs aflag signal /BADk, which is supplied to the disable circuit 120. Thedisable circuit 120 generates a disable signal /DIS for inactivating ablock decoder BDx (where x=0˜m−1) corresponding to the block addressBLK_Add in the row decoder 140. In order to produce the flag signal/BADk, the repair controller 110 may include a bad block addressregister 111, which stores addresses of bad blocks. During an initialoperation of the flash memory device 100, the bad block addresses may beread from an initial data region of a cell array 150 and stored in thebad block address register 111.

The disable circuit 120 generates the disable signal /DIS for preventingselection of a block decoder BDx (e.g., BD2) corresponding to a badblock and/or a bad block address. When the flag signal /BADk isactivated, the disable signal /DIS may be generated to prevent a memoryblock from being selected.

The predecoder 130 may decode a block address BLK_Add and generate blockselect signals Pi, Qi and Ri for selecting a memory block. The rowdecoder 140 selects a memory block in response to the block selectsignals Pi, Qi and Ri from the predecoder 130. When the disable signal/DIS is activated, the predecoder 130 generates block select signals Pi,Qi and Ri to inactivate a memory block corresponding to the input blockaddress Pi, Qi and Ri.

The row decoder 140 may select a memory block and a page in response toa row address. In particular, the row decoder 140 may select a memoryblock and a page in response to the block select signals Pi, Qi and Ri.One of the pages in a selected memory block may be selected by a pageaddress. However, each block decoder in the row decoder 140, accordingto the present embodiment, does not include a storage element (e.g.,fuse or latch) indicating a bad block. An inactive operation to a badblock may be carried out only based on the block select signals Pi, Qiand Ri. A structure of respective block decoders BDO to BDm−1 in the rowdecoder 140 will be more fully described with reference to FIG. 3,below.

The cell array 150 includes multiple memory blocks MCBx (where x=0˜m−1),which are connected to corresponding block decoders DBx in the rowdecoder 140, respectively. The cell array 150 may include defectivememory cells from the process level. A memory block having defectivememory cell(s) is called a bad block, such as bad block MCB2, forexample, which may be connected to corresponding block decoder BD2.

A page buffer 160 may program memory cells in a selected page, or maysense and amplify data stored in memory cells in a selected page. Thatis, the page buffer 160 may operate as a write driver or as a senseamplifier based upon a mode of operation. For example, in a read mode ofoperation, the page buffer 160 may sense and store data stored inselected memory cells (e.g., memory cells in a selected page).

A peripheral block 170 performs a data input/output operation,generating, for example, a ready/busy signal RnB, a pass/fail checkoperation, etc. when a bad block is selected. The flash memory device100, according to the embodiment of the present invention, does notinclude redundant cells for replacing bad blocks. Accordingly, it isnecessary to inform external systems, such as a memory controller (notshown), that an input block address BLK_Add is an address of a badblock. The peripheral block 170 may control the page buffer 160 or avoltage generator (not shown) to prevent an operation corresponding to acommand input together with a bad block address. The peripheral block170 informs the external system that an address corresponding to a badblock is input. A detailed description of the peripheral block 170follows.

A data output buffer 171 may prevent data from being output in responseto the flag signal /BADk. Alternatively, when the flag signal /BADk isactivated, the data output buffer 171 may output fixed data indicatingthat a bad block is selected. For example, the data output buffer 171may output page data consisting of data “1” of an erase state during adata output cycle.

A ready/busy (RnB) generator 172 is capable of outputting an indicationthat a block address BLK_Add corresponds to a bad block, via aready/busy signal RnB. While fixed data is output from the data outputbuffer 171, the ready/busy generator 172 is capable of outputtingexternally that a bad block address has been input. Alternatively, whilea data output operation of the data output buffer 171 is interrupted,the ready/busy generator 172 is capable of sending an indication that abad block address is input. For example, when the flag signal /BADk isactivated, the ready/busy generator 172 may set the ready/busy signalRnB to a busy state “BUSY.” Alternatively, during a data output cycle,the read/busy generator 172 may be set to output the read/busy signalRnB having a busy state “BUSY.” As a result, a memory controller (notshown) may select another memory block with reference to a state of theready/busy signal RnB. In various embodiments, indications of whether abad block address has been input can be provided externally using onlyone of the data output buffer 171 and the ready/busy generator 172.

A program/read/erase controller 173 may interrupt a program, read orerase operation of a cell region corresponding to a block addressBLK_Add in response to the flag signal /BADk. It is therefore possibleto prevent generation of high voltages for a program, read or eraseoperation or a bit line setup operation of the page buffer 160, forexample. These interruption operations may be made organically, forexample, by generating the read/busy signal RnB.

A pass/fail check part 174 is configured to check whether data ofprogrammed or erased memory cells is pass data. In the disclosedembodiment, it is possible to use the pass//fail check part 174 toinform internal control logic that an input address corresponds to a badblock, in response to the flag signal /BADk.

In accordance with the above-described flash memory device, it ispossible to prevent accessing a bad block, without incorporating a fuse,a latch or other storage element in each block decoder of the rowdecoder 140, for indicating the bad block. When an address correspondingto a bad block is input, the flash memory device 100 may outputinformation (e.g., RnB and/or fixed data) externally indicating that abad block has been selected. Accordingly, it is possible to cope with abad block by confirming the output information (e.g., RnB and/or fixeddata) and selecting a different memory block.

FIG. 3 is a circuit diagram showing a block decoder illustrated in FIG.2, according to an illustrative embodiment of the present invention.

Referring to FIG. 3, the row decoder 140 may include block decoders BD0to BDm−1, respectively corresponding to memory blocks. Each of the blockdecoders BD0 to BDm−1 does not include a storage element indicating abad block. For example, a block decoder BDx does not have a fuse cut incase of a bad block or a latch for interrupting transferring of blockselect signals Pi, Qi and Ri. Accordingly, the row decoder 140 mayoccupy less chip area than that of a convention row decoder having fusesor latches.

Referring to FIG. 3, if block select signals Pi, Qi and Ri are allactivated, node N4 is set to a high level, and switch transistor NM fordisabling a string select line SSL is cut off. A high-voltage switch 144drives a block word line BWL with a high voltage based on a logic valueof the node N4. Whether a memory block is selected may thus bedetermined only by block select signals Pi, Qi and Ri. Accordingly, ablock decoder BDx of the present invention does not require a fuse, alatch or other storage element.

FIG. 4 is a circuit diagram showing a disable circuit illustrated inFIG. 2, according to an illustrative embodiment of the presentinvention.

Referring to FIG. 4, the disable circuit 120 includes four NAND gatesfor receiving input flag signals /BADk (k=1˜16). Each output is providedto NOR gate 125, which outputs a disable signal /DIS if any one of flagsignals /BADk (k=1˜16) corresponding to bad blocks is activated. In thedepicted example, the disable circuit 120 activates the disable signal/DIS at a low level. Although the example depicts 16 bad blocks, it isapparent to one skilled in the art that the number of bad blocks is notlimited to this example.

FIGS. 5A to 5C are circuit diagrams showing a predecoder illustrated inFIG. 2, according to illustrative embodiments of the present invention.The predecoder 130 is structured under the assumption that a blockaddress BLK_Add consists of address bits A13˜A21. Referring to FIG. 5A,block select signals P1˜P8 may be obtained by decoding three addressbits A12, A13 and A14, for example.

FIG. 5B shows part of the predecoder 130 for decoding address bitsA15˜A17 and generating block select signals Q1˜Q8. A disable signal /DISmay be applied to respective NAND gates 133˜134 for decoding addressbits A15˜A17. Accordingly, block select signals Q1˜Q8 may be set to alow level when the disable signal /DIS is activated low (logic “0”).FIG. 5C shows part of the predecoder 130 for decoding address bitsA18˜A21 and generating block select signals R1˜R16.

In accordance with the exemplary configuration of the predecoder 130,when the disable signal /DIS is activated, the block select signalsQ1˜Q8 may be set to a low level, so that selection of a memory blockcorresponding to a block address BLK_Add may be interrupted.

FIGS. 6A to 6C are timing diagrams illustrating exemplary read, programand write operations of a flash memory device, according to illustrativeembodiments of the present invention.

As more fully described below, examples are provided showing use of aready/busy signal RnB to inform an external system that an addresscorresponding to a bad block has been received. FIGS. 6A to 6Cillustrate examples in which the ready/busy signal RnB is set tomaintain a ready state “READY” when a flag signal /BADk is activated.

FIG. 6A is a timing diagram showing an exemplary variation of aready/busy signal RnB during a read operation. When any one of themultiple flag signals /BADk is activated, the ready/busy generator 172causes the ready/busy signal RnB to be retained in a ready state“READY.” In comparison, if an address is received in a conventionalflash memory device, the ready/bus signal RnB goes to a busy state“BUSY” following an input of an address, as illustrated by a dashed linein FIG. 6A, and then transitions to the ready state “READY.” At thistime, read-out data may be output to an I/O bus. In the flash memorydevice according to embodiments of the present invention, when the flagsignal /BADk is activated, the ready/busy signal RnB is retained in theready state “READY” without transition into the busy state “BUSY.” Basedon the state of the ready/busy signal RnB, a memory controller (notshown) is able to confirm that the address provided to the flash memorydevice corresponds to a bad block and to select a different memoryblock.

FIG. 6B is a timing diagram showing an exemplary variation of aready/busy signal RnB during a program operation. Generally, aready/busy signal RnB may be set to output a busy state “BUSY” followingan input of address and program data, as illustrated by a dashed line inFIG. 6B. In contrast, in the flash memory device according toembodiments of the present invention, when the flag signal /BADk isactivated, the ready/busy signal RnB is retained in the ready state“READY” without transition to the busy state “BUSY.” Based on the stateof the ready/busy signal RnB, a memory controller (not shown) is able toconfirm that the address provided to the flash memory device correspondsto a bad block and to select a different memory block.

FIG. 6C is a timing diagram showing an exemplary variation of aready/busy signal RnB during an erase operation. Referring to FIG. 6C,when a block address BLK_Add input for an erase operation corresponds toa bad block, a flag signal /BADk may be activated, as illustrated inFIG. 6C. The program/read/erase controller 173, for example, mayinterrupt a required erase operation in response to activation of theflag signal /BADk. The ready/busy generator 172 retains the ready/busysignal RnB in a ready state “READY” in response to activation of theflag signal /BADk. In other words, there is no transition to a busystate “BUSY,” illustrated by the dashed line. A memory controller (notshown) is able to confirm selection of a bad block based on theready/busy signal RnB being in the ready state “READY,” and the eraseoperation of a selected memory block is interrupted.

Based on the above-described exemplary operations of the peripheralblock 170, as depicted in FIGS. 6A to 6C, it is possible to confirm whena bad block is selected. Accordingly, the memory controller (not shown)is capable of selecting a normal memory block instead of a bad block.

FIGS. 7A to 7C are timing diagrams illustrating exemplary operations ofthe peripheral block 170, in which a ready/busy signal RnB is maintainedin a busy state “BUSY” upon activation of a flag signal /BADk.

FIG. 7A is a timing diagram showing an exemplary variation of aready/busy signal RnB during a read operation. When a flag signal /BADkis activated, the program/read/erase controller 173 interrupts a dataread-out operation with respect to the cell array 150, and the dataoutput buffer 171 is disabled so data is not output. At this time, theready/busy generator 172 retains a ready/busy signal RnB in a busy state“BUSY” during a data output cycle, as illustrated by the solid line. InFIG. 7A, the dashed line indicates a state of the ready/busy signal RnBwhen a normal memory block is accessed.

FIG. 7B is a timing diagram showing an exemplary variation of aready/busy signal RnB during a program operation. When a flag signal/BADk is activated, the program/read/erase controller 173 interrupts adata write operation with respect to the cell array 150. The ready/busygenerator 172 retains the ready/busy signal RnB in a busy state “BUSY”during a normal program cycle, as illustrated by the solid line in FIG.7B. In FIG. 7B, the dashed line indicates a state of the ready/busysignal RnB when a normal memory block is accessed.

FIG. 7C is a timing diagram showing an exemplary variation of aready/busy signal RnB during an erase operation. When a flag signal/BADk is activated, the program/read/erase controller 173 interrupts anerase operation with respect to a memory block that corresponds to ablock address BLK_Add. The ready/busy generator 172 causes theready/busy signal RnB to be set to a busy state “BUSY” during a normalerase cycle, as illustrated by the solid line in FIG. 7C. In FIG. 7C,the dashed line indicates a state of the ready/busy signal RnB when anormal memory block is accessed.

As indicated by the timing diagrams of FIGS. 7A to 7C, if an addresscorresponding to a bad block is input, an internal operationcorresponding to an input command may be interrupted. At this time, theready/busy generator 172 maintains the ready/busy signal RnB in a busystate “BUSY” during a corresponding cycle. It is thus possible for usersto recognize selection of a bad block based on the state of theready/busy signal RnB. Further, it is possible for users to select anormal memory block instead of a bad block, in order to again perform aprogram/read/erase operation.

FIG. 8 is a timing diagram illustrating an exemplary read operation of aflash memory device, according to illustrative embodiments of thepresent invention. When a flag signal /BADk is activated, the dataoutput buffer 171 outputs fixed data indicating selection of a badblock, instead of data sensed and latched by the page buffer 160. Atthis time, the ready/busy generator 172 and the program/read/erasecontroller 173 may operate normally. Although not shown in the figures,it is possible to load the fixed data to the data output buffer 171 froman additionally prepared latch circuit and to output the loaded datafrom the data output buffer 171. Accordingly, it is possible to detectwhether a bad block has been selected, based on fixed data transferredvia an input/output bus instead of the ready/busy signal RnB.

It is understood that the previously described embodiments of thepresent invention use a flash memory device that does not have aredundant block. However, a redundant block can be provided in a flashmemory device together with a row decoder structure, as illustrated inFIG. 2, for example.

FIG. 9 is a block diagram showing a flash memory device, according toanother illustrative embodiment of the present invention. Referring toFIG. 9, a flash memory device 200 includes a main row decoder 240 and aredundant row decoder 270. The main row decoder 240 does not include astorage element, such as a fuse or latch, for indicating a bad block.The flash memory device 200 further includes a repair controller 210, adisable circuit 220 and a predecoder 230. The repair controller 210 iscapable of performing a repair operation with respect to a bad block.

For example, the repair controller 210 is configured to detect whetheran input block address BLK_Add corresponds to a bad block. When a blockaddress BLK_Add corresponds to a bad block, the repair controller 210may output a flag signal /BADk indicating that the block address BLK_Addis a bad block. The repair controller 210 generates a repair signal REPjfor selecting a redundant block decoder RBDj that corresponds to theblock address BLK_Add. The repair controller 210 may include a bad blockaddress register 211 for storing bad block addresses and a redundantblock address register 212 for storing redundant block addresses. Duringan initial operation of the flash memory device 200, bad block addressesmay be read out from an initial data region of a cell array 250 andstored in the bad block address register 211.

The disable circuit 220 generates a disable signal /DIS that is used toinactivate a block decoder (e.g., BD2) of the main row decoder 240corresponding to a bad block. The disable circuit 220 may activate thedisable signal /DIS to prevent selection of a memory block when the flagsignal /BADk is activated. Alternatively, the disable circuit 220 mayactivate the disable signal /DIS when a repair signal REPj for switchinga bad block to a normal block is activated. A detailed description withrespect to the disable circuit 220 follows with reference to FIG. 10.

The predecoder 230 decodes a block address BLK_Add and generates blockselect signals Pi, Qi and Ri for selecting a memory block. The blockselect signals Pi, Qi and Ri may be sent to the main row decoder 240 toselect a memory block. However, if the disable signal /DIS is activated,the predecoder 230 may generate the block select signals Pi, Qi and Rito interrupt selection of a memory block that corresponds to an inputblock address BLK_Add.

The main row decoder 240 selects a memory block and a row in response toa row address. In particular, the main row decoder 240 may includemultiple block decoders BDx, (e.g., BD0˜BDm−1), each of which selects acorresponding memory block and a row in the corresponding memory blockin response to a row address. For example, each of the block decodersBDx may select a memory block in response to block select signals Pi, Qiand Ri and select a row in the selected memory block in response to apage address. In accordance with the present embodiment, each blockdecoder BDx of the flash memory device does not include a fuse or alatch or other storage element used to indicate a bad block. This isbecause selecting and interrupting operations with respect to bad blocksare performed by the block select signals Pi, Qi and Ri. Each blockdecoder BDx may be structured as shown, for example, in FIG. 3.

The main cell array 250 may include multiple memory cells arranged inrows (e.g., word lines) and columns (e.g., bit lines). The memory cellsconstitute multiple memory blocks MCB0˜MCBm−1 that correspond to theblock decoders BD0˜BDm−1 in the main row decoder 240, respectively.

A page buffer 260 may program memory cells in a selected page of aselected memory block, or sense and amplify data stored in the memorycells of the selected page. That is, the page buffer 260 may act as awrite driver or a sense amplifier based up on a mode of operation. Forexample, the page buffer 260 may sense and store data stored in selectedmemory cells during a read mode of operation. If the flag signal /BADkis activated, the page buffer 260 may sense and amplify memory cells ina selected page of a redundant block (e.g., RMCB0) in which a bad block(e.g., MCB2) is placed.

A redundant row decoder 270 and a redundant cell array 280 may have thesame structure as the main row decoder 240 and the main cell array 250,respectively. Redundant block decoders RBD0˜RBDn−1 in the redundant rowdecoder 270 may be selected by repair signals REPj (where j=0˜n−1) fromthe repair control block 210, respectively.

An illustrative embodiment of a flash memory device, including redundantmemory blocks, has been described above with reference to accompanyingdrawings. As described, the flash memory device 200 is capable ofinterrupting access to a bad block, without including a storage element(e.g., fuse or latch) used to indicate the bad block. That is, the badblock is switched to a corresponding redundant block under control ofthe repair controller 210.

FIG. 10 is a circuit diagram showing a disable circuit illustrated inFIG. 9, according to an illustrative embodiment of the presentinvention. For convenience of description, it is assumed that the flashmemory device 200 includes 16 bad blocks and two redundant blocks.

Referring to FIG. 10, the disable circuit 220 includes NAND gates 221,222, 223, 224 and 225 and NOR gate 226, which are connected asillustrated in FIG. 10. In accordance with this exemplary configurationof the disable circuit 220, a disable signal /DIS may be activated inresponse to any one of flag signals /BAD1˜/BAD16 or repair signalsREP1˜REP2 being activated. In the depicted example, the disable circuit220 activates the disable signal /DIS at a low level. As stated above,although the example depicts 16 bad blocks and two redundant blocks, itis apparent to one skilled in the art that the number of blocks is notlimited to this example.

FIG. 11 is a block diagram showing a memory card including a flashmemory device, according to illustrative embodiments of the presentinvention. Referring to FIG. 11, a memory card 300 supports alarge-volume data storing capacity, and may include flash memory device310, according to embodiments of the present invention. The memory card300 may further include a memory controller 320 configured to controldata exchanges between a Host and the flash memory device 310. The flashmemory device 310 may include block decoders, none of which include afuse or latch for indicating bad blocks. The memory controller 320 maybe configured to detect whether an address provided to the flash memorydevice 310 corresponds to a bad block, based upon input/output data or aready/busy signal RnB, as described above.

Static random access memory (SRAM) 321 may be used as a work memory of aprocessing unit 322 (e.g., CPU). A host interface 323 may include a dataexchange protocol of a host connected with the memory card 300. An errorchecking and correcting (ECC) block 324 may be used to detect andcorrect errors in data read from the flash memory device 310 that iscapable of storing single bit data and/or multi-bit data. A memoryinterface 325 may be configured to interface with the flash memorydevice 310. The processing unit 322 may perform an overall controloperation for data exchange of the memory controller 320. Although notshown in figures, it would be apparent to one skilled in the art thatthe memory card 300 may further include read only memory (ROM), forexample, used to store code data for interfacing with the host.

As set forth above, the flash memory device and memory system arecapable of repairing bad blocks without using fuses or latches in blockdecoders. Accordingly, it is possible to reduce the size of row decodersand to improve the reliability of flash memory devices and memorysystems including the flash memory devices.

While the present invention has been described with reference toexemplary embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the present invention. Therefore, it shouldbe understood that the above embodiments are not limiting, butillustrative.

1. A flash memory device comprising: a plurality of memory blocks; adecoder configured to select at least one of the plurality of memoryblocks in response to block select signals; a controller configured togenerate the block select signals in response to a block address and togenerate a flag signal when the block address corresponds to a badblock; and a data output buffer configured to output fixed data inresponse to the flag signal, indicating that the block addresscorresponds to the bad block, wherein, when the block addresscorresponds to the bad block, the controller generates the block selectsignals to cause the decoder to interrupt selection of the memory blockcorresponding to the block address.
 2. The flash memory device of claim1, wherein the decoder has no storage element for storing bad blockinformation.
 3. The flash memory device of claim 1, wherein thecontroller comprises: a repair controller configured to generate theflag signal when the block address corresponds to the bad block; adisable circuit configured to generate a disable signal in response tothe flag signal; and a predecoder configured to generate the blockselect signals in response to the block address, wherein the predecodergenerates the block select signals to inactivate the bad block when thepredecoder receives the disable signal.
 4. The flash memory device ofclaim 3, wherein the repair controller comprises an address registerthat stores block addresses of bad blocks.
 5. The flash memory device ofclaim 1, further comprising: a memory for storing the fixed data.
 6. Theflash memory device of claim 1, further comprising: a program/read/erasecontroller configured to interrupt one of a program/read/erase operationwith respect to the memory block corresponding to the block address inresponse to the flag signal.
 7. The flash memory device of claim 1,further comprising: a pass/fail detector configured to indicate a failstate in response to the flag signal.
 8. A method of managing a badblock in a flash memory device, comprising a memory block and a blockdecoder for selecting the memory block in response to a block selectsignal, the method comprising: comparing an input block address with abad block address, which indicates a defective memory block; generatinga flag signal when the input block address corresponds to the bad blockaddress; and outputting fixed data having a predetermined bit value viaan input/output pin to indicate that the input block address correspondsto the bad block address, wherein the block decoder does not include astorage element for indicating the defective memory block.
 9. The methodof claim 8, further comprising: interrupting an internal operationcorresponding to a command input with the input block address.
 10. Amemory system comprising: a flash memory device outputting a fixed dataor a ready/busy signal in response to a block address corresponding to abad block; and a memory controller configured to detect whether theblock address provided to the flash memory device corresponds to the badblock, based upon the fixed data or the ready/busy signal.
 11. Thememory system of claim 10, wherein the flash memory device comprises: aplurality of memory blocks; a decoder configured to select at least oneof the plurality of memory blocks in response to block select signals; acontroller configured to generate the block select signals in responseto the block address and to generate a flag signal when the blockaddress corresponds to the bad block; and a data output bufferconfigured to output the fixed data in response to the flag signal,indicating that the block address corresponds to the bad block, wherein,when the block address corresponds to the bad block, the controllergenerates the block select signals to cause the decoder to interruptselection of the memory block corresponding to the block address. 12.The memory system of claim 11, wherein the flash memory device furthercomprises a ready/busy generator configured to output the ready/busysignal having a predetermined pulse width indicating that the blockaddress corresponds to the bad block.
 13. The memory system of claim 11,wherein the decoder has no storage element for storing bad blockinformation.
 14. The memory system of claim 11, wherein the controllercomprises: a repair controller configured to generate the flag signalwhen the block address corresponds to the bad block; a disable circuitconfigured to generate a disable signal in response to the flag signal;and a predecoder configured to generate the block select signals inresponse to the block address, wherein the predecoder generates theblock select signals to inactivate the bad block when the predecoderreceives the disable signal.
 15. The memory system of claim 14, whereinthe repair controller comprises an address register that stores blockaddresses of bad blocks.
 16. The memory system of claim 11, wherein theflash memory device further comprises: a memory for storing the fixeddata.
 17. The memory system of claim 11, wherein the flash memory devicefurther comprises: a program/read/erase controller configured tointerrupt one of a program/read/erase operation with respect to thememory block corresponding to the block address in response to the flagsignal.
 18. The memory system of claim 11, wherein the flash memorydevice further comprises: a pass/fail detector configured to indicate afail state in response to the flag signal.